Water dispensers are configured such that when a user operates a lever or a cock, thereby opening a valve, water in the water storage tank is discharged through a water discharge line, and is received in e.g. a user's cup. One of such water dispensers includes a raw water container provided at the lower portion of the housing, and a water storage tank provided at a higher position than the raw water container. This type of water dispenser is advantageous in that when exchanging the used raw water container with a new one, a user or an operator does not have to lift the new raw water container to a high place. Since the water storage tank is provided at a higher position than the raw water container, this water dispenser includes a water supply line in which a pump is provided to lift water in the raw water container into the water storage tank through the water supply line. When water in the water supply tank decreases, the pump is automatically activated to lift water in the raw water container into the water supply tank until the water in the water storage tank increases to a predetermined amount (see e.g. Japanese Patent 4802299B and Japanese Patent Publication 2001-153523A).
A water dispenser of the type in which the raw water container is placed upside down includes a piercing member which is configured to push up the plug of the raw water container with the container placed upside down. The water supply line has an end portion which is a portion of the piercing member. Most ordinarily, by lowering the raw water container with the plug in contact with piercing member, the plug is pushed up into the container. However, in another arrangement, as in Japanese Patent 4802299B, a piercing member is lifted with the raw water container kept stationary to push in the plug. In either case, by piecing the piercing member through the plug, the raw water container is opened, and simultaneously, the interior of the container is connected to the water supply line.
In the water dispenser disclosed in Japanese Patent 4802299B, since the raw water container, water supply line and water storage tank are connected together in a sealed arrangement, if a rigid container is used as the raw water container, it will be necessary for the pump to generate a large force in order to lift water in the raw water container. Thus, as described in paragraphs [0021] and [0022] of Japanese Patent Publication 2001-153523A, it is preferable to use a raw water container which is made of a soft material and collapsible as water remaining in the container decreases.
Even if a soft raw water container is used, however, in the arrangement in which the raw water container is placed upside down as in Japanese Patent 4802299B, when, with a reduction in water remaining in the container, the raw water container is collapsed such that its peripheral portion is folded until its height decreases to near the mouth of the container, the rigidity of the peripheral wall portion tends to become higher than the atmospheric pressure. Since the container is not collapsible thereafter, the load on the pump tends to increase.